ENGINEERING. 



EVENTS OF 1886. 



323 



poses or for lines connecting suburban districts 

 with cities it appears to possess peculiar ad- 

 vantages. As has been intimated, either elec- 

 tricity or steam may be used for the motor ; 

 but even with mule- or horse-power the sys- 

 tem is found to offer advantages over ordinary 

 roads and tramways. Experiments have fixed 

 the coefficient of adherence at one fifth with 

 14-inch driving-wheels. A locomotive weigh- 

 ing 2,200 pounds, therefore, exerts a tractive 

 force of 440 pounds, and, considering the size 

 of the drivers, this is no mean performance. 

 "With larger drivers the tractive efficiency 

 might be indefinitely increased. With a steam 

 pressure of 100 pounds to the square inch, 

 such an engine will haul, at a speed of 6 miles 

 an hour, about 70 tons on a level, 18 tons on 

 an incline of 1 in 100, 9 tons on an incline of 

 1 in 50, and 6 tons on an incline of 1 in 38. 

 With a lighter load a speed of 10 or 15 miles 

 an hour may be safely attained, and with 

 heavier rolling-stock and equipment, such as 

 would naturally be used in actual service, a still 

 higher speed and heavier loads can be handled. 



Bartholdi's Statne of Liberty. In its pictur- 

 esque aspects, this remarkable work of art is 

 fully described elsewhere. Its construction, 

 however, involves numerous problems that be- 

 long to the engineer rather than to the artist. 

 The external contour of the figure, as it ap- 

 pears to the spectator, consists of copper plates 

 about / 2 of an inch thick, and incapable of 

 sustaining for a moment even the mere con- 

 stant of gravity, not to mention the possible 

 strains of wind-pressure from any direction. 

 The stiffening framework was begun by lining 

 each separate section of the statue with a net- 

 work of iron bars (f by 2 inches) bent so as to 

 conform closely to the curves of the figure. 

 These bars were fastened to the sections by 

 copper bands, riveted in place, and from them, 

 at thousands of points, the strains were dis- 

 tributed to the central supporting frame. The 

 general form of the frame is shown in the two 

 elevations (front and side given herewith). 

 It consists of four heavy corner-posts of angle- 

 iron, joined by horizontal angle-pieces, which 

 divide it into panels, further strengthened by 

 diagonal braces and by struts which are ex- 

 tended so as to approximate more closely the 

 contour of the figure. The extensions, again, 

 are united by braces and girders, and, on one 

 side of the figure, are carried up into what 

 may be termed a u flying truss," to support the 

 arm and torch. In this arm-truss, it will be 

 seen, the panels become smaller and the brac- 

 ing correspondingly lighter. The whole of 

 the frame was designed and put together in 

 Paris by the consulting engineer, M. Eiffel. It 

 was taken apart and shipped to America after 

 having sustained the required tests. 



The engineering work connected with the 

 base and pedestal was intrusted to the late Gen. 

 ( . P. Stone, formerly an officer of the U. S. 

 Ordnance Corps. The architectural design of 

 the pedestal was furnished by Richard M. Hunt. 



The site of the statue is Bedlow's Island, the 

 property of the United States Government, 

 and occupied by a star-fort with barracks, 

 built early in the century, and constructed in 

 the most durable manner. Part of the para- 

 pet was temporarily removed to make room for 

 a tramway leading up from the wharf. The 

 terre-plein of the fort was excavated to the 

 natural soil of stiff clay, gravel, and bowlders, 

 and upon this was built up a solid block of 

 concrete, probably the largest in the world. 

 It is 90 feet square at base, 65 feet at top, and 

 is 52 feet 10 inches high. There is a central 

 well-hole 10 feet square leading to four diver- 

 gent archways at the extreme base. Surround- 

 ing the base is a concrete arch 3 feet 6 inches 

 thick, and having a cord-span of 49 feet. This 

 arch supports the ornamental exterior slope of 

 grass and the four flights of steps leading to 

 the terrace which forms the top of the con- 

 crete, and upon which rests the massive ma- 

 sonry of the pedestal proper. The vertical 

 section and plan in the diagram show the es- 

 sentials of construction. The pedestal is a 

 stone tower 43 feet 6 inches square at top, 

 with the corners cut off to form an octagon. 

 The central shaft, 26 feet 6 inches square, 

 descends to the terrace, and contains the an- 

 chorage-works that hold the statue in posi- 

 tion. At about 25 feet from the terrace a 

 system of plate girders, 41 feet long, is built 

 into the masonry. The girders are 4 feet 

 deep, and made of -jj-inch web-plate and heavy 

 angle-irons. At the top of the pedestal is a 

 second similar system of girders, 34 feet long, 

 extending across the well-hole. The two sys- 

 tems of girders are joined by four sets of eye- 

 bars each composed of four bars !$ by 4 inches. 

 They are carried close to the masonry, and 

 incline inward when they clear the top of 

 the pedestal, joining the central frame of 

 the statue at the junction of the first and 

 second panels. Since the completion of the 

 statue it has borne wind-storms of great vio- 

 lence, and from opposite directions, the veloci- 

 ty of the wind registering as high as 75 miles 

 an hour, with an attendant pressure of not far 

 from 15 pounds per square foot of surface. 

 Under such conditions the oscillation even of 

 solid masonry is plainly perceptible, and of 

 course that of comparatively yielding metal 

 must be at least as great. In point of fact, it 

 \vas rather less than had been anticipated by 

 the engineers. The statue is far greater than 

 any in the world of composite construction. 

 In India larger figures exist, hewed from solid 

 rock, in place, and not to be considered in any 

 sense as engineering work. The total weight 

 of the Liberty Statue is 440,920 pounds, of 

 which 176,368 are copper, and the rest iron 

 and steel. 



EJWELOPES. See PAPEE BAGS AOT>ENVELOPES. 



EVENTS OF 1886. In the United States, the 

 labor troubles were the most important and 

 significant events of the year. They involved 

 not only the interests of capital and labor, but 



